ABC News(CHAPEL HILL, N.C.) -- The moment of truth seems to be fast approaching for John Edwards as lawyers involved in the case say federal prosecutors have wrapped up their grand jury investigation and await a decision on whether the former presidential candidate should face criminal charges.

The key question is whether Edwards knew that money from supporters of his 2008 presidential campaign was paid to his mistress to keep her quiet and out of the public eye while he ran for President and she had his baby.

When Edwards announced he was running for President, his mistress, campaign filmmaker Rielle Hunter, was there just a few feet away from Edwards' now deceased wife, Elizabeth.

When the National Enquirer later broke the story of the affair and the baby, Edwards denied any involvement, and two of his big contributors provided tens of thousands of dollars that ended up supporting the mistress.

"The two things that they have to prove would be first, that the money that was paid to this woman was done for the purpose of influencing the election and secondly, that it was done with Mr. Edwards' knowledge or in coordination with him," Gerald Herbert, executive director of the Campaign Legal Center, told ABC News.

Edwards' mistress testified before the grand jury in North Carolina last year, bringing Edwards' daughter, Frances Quinn, along for the session. But the most damning evidence may have come from Edwards' former aide, Andrew Young, who said that at Edwards' request, Young claimed he was the father.

Young told ABC News he was part of an elaborate cover-up Edwards helped to orchestrate, even if he didn't know all the details.

"But he knew about the money. He knew about the methodology. He knew about the sources," Young said.

Young gave prosecutors messages left on his phone by Edwards, seemingly expressing his gratitude for his help in the cover-up.

"I just wanted you to hear that and to once again to tell you I love you…uhh…I really love you Andrew," one of the messages said.

Herbert said that as far as criminal charges, a distinction of intention would have to be made between Edwards spending the money for personal reasons, which is not necessarily a criminal action, and spending money in an attempt to improperly influence the election.

According to lawyers in the case, a decision on the next step will come by the end of the month.

As an indication of just how big a problem Edwards may have, it was revealed Thursday that Edwards had hired one of Washington's top lawyers, Greg Craig, former White House counsel for President Obama who helped defend Bill Clinton over allegations of his affairs. ﻿